#cont{
  position: relative;
  height: 500px;
  overflow: hidden;
}
.imm a{
  position: absolute
}
.imm img{
  width: 100%;
  height: 500px;
}
.btn ul {
  position: absolute;
  z-index: 10000;
  bottom: 40px;
  right: 40%;

}
.btn ul li{
  width: 50px;
  height: 3px;
  background-color: #555555;
  border-radius: 10px;
  list-style: none;
  float: left;
  margin: 0 5px;
  text-align: center;
  color: transparent;
  line-height: 20px;
  cursor: pointer;
}
.btn ul li.on{
  background-color: orange;
}
 #left,#right{
   width: 50px;
   height: 50px;
   z-index: 9999;
   display: block;
   position: absolute;
   top: 50%;
   color: white;
   font-size: 20px;
   line-height: 50px;
   text-align: center;
   border-radius: 50%;
   border: 2px solid white;
 }
#right{
  right: 20px;
  
}
#left{
  left: 20px;
}